Material processing apparatuses, such as laser cutting machines, are widely used in the cutting, welding, and heat treating of materials. A laser-cutting machine generally includes a high-power laser, a nozzle, a gas stream, an optical system, and a computer numeric control (CNC) system. The laser beam and gas stream pass through an orifice of the nozzle and impinge upon a workpiece. The laser beam heats the workpiece, which, in conjunction with any chemical reaction between the gas and workpiece material, alters (e.g., liquefies and/or vaporizes) a selected area of workpiece, allowing an operator to cut or otherwise modify the workpiece. The laser optics and CNC are used to position and direct the laser beam relative to the workpiece during a cutting operation. Lasers are frequently used in material processing applications because laser beams can be focused to small spot sizes, thereby achieving the intensity and power density desired to process industrial-strength materials, such as metals.
In conventional laser cutting systems, alignment of system components (e.g., nozzles) can be critical to system life and performance. For example, alignment of the nozzle bore and/or orifice to the nozzle holder and laser cutting head optics can be critical to proper functioning of the laser cutting process. In addition, alignment of the laser beam and the gas jet can be critical to achieving uniform cut quality around all sides of the workpiece. One instance in which alignment issues manifest is during component replacement and installation, during which the nozzle bore(s) and/or orifice(s) must be aligned with a longitudinal axis of the laser head, and thus the laser beam, so as to avoid non-symmetric gas flow about the beam. The problem is compounded because conventional nozzles must be replaced frequently, and each nozzle replacement can involve a complex installation and verification to prove alignment. In addition, because components must often be replaced in the field, significant machine down time and technician expertise can be required to ensure proper installation and alignment. Field replacement can also require specialized tools to attain, verify, and maintain proper component alignment.
One type of nozzle, a “double nozzle,” has specific benefits for laser cutting applications but also creates unique issues around alignment of component parts. Structurally, a double nozzle typically has two pieces (an inner and an outer nozzle portion) that are press-fitted or threaded together. A primary function of a double nozzle is to create two separate flows of gas within an inner and an outer nozzle portion. One flow of gas is delivered through a central bore and positioned along the axis of the laser beam itself, while a second flow of gas surrounds the central bore and provides a coaxial flow of lower pressure gas. The central flow helps to remove material during the cutting process as the laser beam heats the material and the process gas ejects the material from the kerf, while the lower pressure coaxial flow provides a protective flow around the central flow, preventing entrainment of air into the molten kerf and surrounding the kerf with the correct gas chemistry for the material being processed.
FIG. 1 shows a prior art double nozzle configuration. In this embodiment, a double nozzle 100 includes an inner body portion 102 (inner nozzle portion) and an outer body portion 104 (outer nozzle portion) joined at an interface surface 124. The inner body portion 102 has an orifice 112 that permits the laser beam to pass through the double nozzle 100. The outer body portion 104 has an orifice 114 and an alignment surface 122 for aligning the double nozzle 100 with a laser machining head (not shown). In this configuration, two separate surface interfaces determine alignment of the inner nozzle orifice 112 relative to a longitudinal axis 107 of the laser machining head and thus the laser beam itself: (1) the alignment surface 122 with the laser machining head; and (2) the nozzle interface 124 between the inner body portion 102 and the outer body portion 104.
The inner nozzle orifice 112 of inner body portion 102 in FIG. 1 is smaller than the outer nozzle orifice 114 and is located closer to the laser beam during operation than the outer nozzle orifice 114. Thus, alignment of the inner nozzle orifice 112 can be particularly important to performance and life of the double nozzle 100. The alignment of the inner nozzle orifice 112 with the longitudinal axis 107 of the laser machining head, and thus the laser beam via two separate interfaces, depends on the accuracy and precision of four separate surfaces that create each of these two-surface interfaces. Therefore, a high level of manufacturing precision is required on these four surfaces, as well as installation accuracy and verification to ensure proper life and performance; misalignment in any of these components can have a dramatic impact on alignment of the inner nozzle orifice 112 relative to longitudinal axis 107 of the laser beam. What is needed is a double nozzle configuration that reduces the number of opportunities for misalignment, thereby improving alignment of the laser beam and the nozzle bore and/or orifice, and simplifies installation and operation.